Not getting seven or eight hours of sleep a night won't kill you, new research
shows.

Earlier this year a large-scale study indicated that getting less than seven hours' sleep was associated with an increased risk of heart disease.

Another concluded that people who sleep less than six hours a night are more likely to die before the age of 65.

But a new report, which followed almost 450 middle-aged and elderly women over a 14-year period, found that those who slept between five and six-and-half hours were most likely to still be alive.

It differed from other studies in that it measured sleep using wrist activity monitors, rather than asking people about their sleep habits.

Daniel Kripke, professor emeritus of psychiatry at the University of California San Diego School of Medicine, said: "The surprise was that when sleep was measured objectively, the best survival was observed among women who slept five to 6.5 hours.